Landfill gas loading ramp-up strategies: Acclimatization optimization and long-term oxidation capacity of methane oxidation biosystems

Methane (CH₄) emissions from landfills represent a challenge in global climate mitigation efforts. Methane oxidation biosystems (MOB) offer a low-cost solution for addressing residual and fugitive CH₄ emissions, yet the role of the acclimatization phase has not received enough attention in the technical literature. Here we optimize the acclimatization of compost-based MOBs through controlled landfill gas (LFG) ramp-up strategies. Four identical laboratory-scale columns were subjected to distinct flow increase patterns: exponential, linear, first-order-like, and constant inlet loading. The results showed that exponential and linear strategies accelerated the attainment of 100% CH₄ removal faster than the constant-flow system. Additionally, the axial gas concentration profile revealed that ramp-up strategies influenced the depth required for complete oxidation. Notably, exponential ramp-up led to full CH₄ removal within the first 50 mm of the methane oxidation layer (MOL) when actively aerated, suggesting the potential to significantly reduce its thickness in field systems. An additional 175-day column test, designed to estimate the maximum methane oxidation capacity under increasing loadings, confirmed the benefits of gradual acclimatization. By assuming that the oxidation rate follows the Michaelis–Menten model, the system achieved sustained removal efficiencies (>90%) and reached a maximum oxidation rate ($V_{\max }$) of 3811 g_CH4·m⁻³·d^-1 and a $K_m$ of 12 g_CH4·m⁻³. These findings highlight the importance of ramp-up strategies in designing efficient and more compact MOBs that can quickly attain design loadings.